Bucking bar control for riveting hammers



May 8, 1945- J. A. ROBERTS 2,375,691

BUCKING BAR CONTROL FOR RIVETING' HAMMERS Filed Deo. l, 1942 U "um wu 1 I 0% su@ w l m ATToRNEY Patented May 8, 1945 BUCKING BAR CONTROL FR. RIVETING HAMMERS James A. Roberts, Detroit, Mich., assignor to Chicago Pneumatic Tool Company, New York, N. Y., a corporation of New Jersey Application December 1, 1942, Serial No. 467,531

7 Claims.

This invention relates to riveting assemblies comprising a pneumatic hammer and a bucking bar cooperating to set a rivet. More particularly the invention is concerned with means placing the hammer action under the joint control of the operator holding the hammer and the holder of` the bucking bar. The invention has especialthough not limited application to aircraft riveting tools, which operate on light sheet` metal.

In the use of riveting assemblies of this kind the operators stand on opposite sides of the work. sometimes out of one anothers view. In devices of prior design, the throttle valve is arranged to be under the control of a single operator, either the riveter or the bucker, who usually delays the start of the hammering operation until certain that the other operator is ready. Occasionally it happens that the hammer is started before the rivet is properly backed up, or before the hammer is placed in operative position, in either of which events the work may be damaged. The present invention obviates delays and prevents accidents by positively precluding starting of the hammer until the bucking bar is in position to absorb the blows thereof. I

An object of the invention is to increase the speed and efficiency of the riveting assembly by making the compressed air Asupply subject to control both from the hammer and from thc bucking bar.

A further object is to embody in the hammer a throttle `valve under the control of the hammer operator, and an auxiliary valve in series with the throttle valve and controlled from the bucker.

Still another `object of the invention is to connect the hammer and the bucking bar by a ilexible Bowden type cable adapted to transmit the motion of manipulative means on the bucking bar to the auxiliary valve in the hammer.

` A feature of the invention is that the auxiliary valve is contained in a, fitting which together with the interconnecting Bowden cable may be mounted as an attachment on riveting hammers already in use.

Other objects and structural details of the invention `will be apparent from the following description when read in conjunction with the accompanying drawing, wherein:

Fig. 1 is a view, partly in side elevation and partly in longitudinal section, of ariveting assembly comprising the invention; and

Fig; 2 is a view of the bucking bar in cross section, being taken substantially along the line 2-2 of F18. 1.

Referring to the drawing, a riveting assembly in which the invention may` beembodied comprises a pneumatic hammer II of a type finding `particular favor in the aircraft industry where it is used to upset small aluminum alloy rivets. The hammer is made up of a cylinder I2 and an offset handle I3. 'I'he cylinder houses a motor including a reciprocable piston I4 and means for directing pressure fluid alternately to the ends thereof, while the handle is formed with an air inlet I5 and throttle means operating under the control of a trigger I 6. The piston I4 acts as a hammer, delivering impacts to an anvil I1 which extends beyond the front end of the cylinder for engagement with the work. The work, in this instance, is represented by overlapping plates I8 and I9 which are fastened together by rivets to form part of an airplane skin covering. Guide holes in the work receive rivets, as the one indicated at 2|, the rivets being disposed with preformed heads contacting the work on one side thereof and shank portions projecting from the opposite side. According to one method of riveting, the anvil I1 is pressed against the preformed head on the rivet while the shank portion is engaged on the opposite side of the work by a bucking bar 22. When the hammer is started percussive impulses are delivered to the work through the anvil I1 and are sustained by the bucking bar 22. Forward pressure being exerted by the bucking bar throughout the operation the reaction of the hammer blows serves to upset the shank of the rivet, a flat or curved head being thereby formed on the side ofthe work opposite the preformed head.

It is important that the skin surface be not marred or scratched by a premature hammer action. Therefore care must be exercised by the separate operators holding the hammer and tbe bucking bar that the ends of the rivet are prop erly engaged before the hammer is started. The present invention aims to guard against the misoperation resulting from a lack of such engagement by placing the compressed air suppy under the joint control of both operators. Thus the piston I4 cannot begin its motion until the operators of the hammer and bucking bar signify by releasing the air supply that their respective implements are in working position.

The air inlet I5 is part of a pressure duid supply passageway including passages 23 and 24 connected through a bore 25. Within the bore 25 is a bushing 26 having ports registering respectively with passages 23 and 24. Communi cation between passages 23 and 24 is controlled by a valve 21 in bushing 24. The valve 21 is pressed bya spring 28 to a seat 29'between the ported areas of the bushing and so normally prevents the ilow of fluid to the passage 24 and thereby to the hammer cylinder. The valve 21 has a stem extending upward through and beyond the bushing 26, the upper end of the stem underlying one .arm of a lever 3l. The lever 3I is pivotally mounted at 32 within a recess in the handle I3 and is engaged with the trigger I6. When the trigger is pulled rearward the lever 3I,` rocking upon its pivot 32, unseats the valve 21 whereupon air from inlet I5 and passage 23 is allowed to iiow through the bushing 28 and into passage 24 where it is directed to the motor, thereby initiating operation of the hammer.

' Heretofore, air has been supplied to the inlet I by a flexible hose line coupled directly thereto. According to this invention, however, there is placed between the inlet I5 and a hose line 33 a fitting in the form of an auxiliary valve housing 34. The housing 34 has a tubular portion 35 extending into the inletl I5 in threaded connection with a bushing 36. The body of housing 34 defines a chamber 31 receiving air from the hose line 33 and communicating with the interior of tubular portion 35 by way of a passage 38. Controlling the flow of air from chamber 31 to passage 38 is a valve 39, the head of which lies within the chamber 31 while va stem portion extends through the passage 38 and into a split projection 4I on the housing. The head of valve 39 is adapted to occupy a seat on the peripheral edge of passage 33 and so cut off the now of fluid from chamber 31 to tubular portion 35 and inlet I5. Thus, the supply of air to the hammer is under the dual control of the throttle valve 21 and the auxiliary valve 39, either or both of which when closed will cut off the fluid iiow and so prevent operation of the hammer. The valves 21 and 39 may be said to be arranged in series. Opening of the valve 39 is accomplished by remote control from the bucking bar 22. Extending between the hammer and bucking bar is a ilexlilole Bowden type cable 42 made up of a wound sheath -43 and an inner wire or core 44. At its onev end the cable 42 is received in the split projection 4I of housing 34 and at its other end extends through a similar projection 45 on the bucking bar into a transverse bore 46 therein. Screws 41 and v48 in the respective split portions 4I and 45 provide a means of clamping the ends of the cable Within the implements. 'Ihe core 44 is movable longitudinally within the sheath 43 and is arranged with its opposite ends projecting beyond the sheath. One end of the core 44 is secured to the stem of valve 39, as by soldering or brazing, While the other end of the core extends outside the bore 46 and is fastened to a lever 49 by a set'screw 5I. The lever 49 is pivotally connected to the bucking bar by a cross pin 52 and serves as a manipulative means for actuating the Bowden cable. Upon depression of the lever 49 the core 44 acts as a plunger on valve 39 moving it to an unseated or open position and allowing the air to iiow from chamber 31 to inlet l5. From there, if the throttle valve 21 is opened, the air may enter the motor supply passages and reciprocation of the hammer piston will begin. The valve 39, core 44 and actuating lever 49, being secured together, comprise an assembly and spring pressure may be applied at any point in the assembly to maintain the valve normally provided by Seuil?. spring 43 surrounding the con 44 beneath thelever 4 3' and seated in a counterbore I4 in the buckingbar.

The cable 42 is otlmlngth thatitmay be passed around the work oir tlimnugh am opening therein and allow freedom on movement oi' the respecclosed. In the present instance such pressure is tive tools at itsA emita. The: bucking bar operator holds the lever'4`97 witlliiim his grasp'rand, when the bar has been brought to bear against the shank of the rivet, depress'es; the lever to open auxiliary valve 39. Their,7 where the throttle valve 21 in the hammer is opened, the assembly will begin the work of setting: the rivet. Opening of the throttle valve l-E- before the bucking bar is engaged with the rivet will not, as in the past, -cause a misoperation off the assembly since the hammer remains inactivef until the operator of the bucking bar signals his readiness by depression oi the lever 49. Considering the lever 49 as a trigger. both triggers I9 anni 492" must be compressed before the hammenem dhive the rivet. The e'orts of the operators as; sa team are thereby synchronized, and the sidl and efficiency of their work are increased.

What is claimddlisx l. A riveting assembly; comprising a uid pressure operated hammer,y abucking bar, said hammer and said ban under separate control and adapted to engage the rivet on opposite sides of the work, a supply passage conducting pressure fluid to said hammer,l a pair of independently operable valves controlling the iiow of fluid through said passage, such now being cut on when either or both of said valves are closed thereby preventing. operation of the hammer, means on said hammer for opening one of said valves, and remote control means. operated from said bucking bar for opening the other of said valves.

2. A riveting assembly, comprising a fluid pressure operated hammer, a bucking bar, said hammer and said bar beig carried by. separate oper- 'ators and adapted to engage the rivet on opposite sides of the work, and means placing the operation of said hammer under the joint control of said operators to guard against damage resulting from a premature hammer action, said means comprising a first iiuid pressure control valve and means on the hammer for opening said ilrst valve, and a second iiuid pressure controlfvalve in series with said rst valve and means on the bucking bar for opening said second valveithe means on said bucking bar acting through a ilexible cable comprising a sheath attached at one end to said hammer and at the other end to said bar and containing a reciprocable core.

3. A riveting assembly, comprising a fluid pressure operated hammer, a bucking` bar, said hammer and said bar being under separate control and adapted to engage the rivet onopposite sides of the work, a supply passage conducting pressure uid to said hammer, a throttle valve asso-l ciated with said hammer for controlling the iiow of fluid through said supply passage, an auxiliary valve for controlling the ow of fluid through said passage, said valves cooperating to cut off `the now of fluid to said hammer when either or both of said valves are closed, and actuating means for said auxiliary valve in the form of a nexible cable connecting said. hammer and said bucking bar, said cable having a longitudinally movable core operable as a plunger from said bucking bar and extending into cooperative relation with said auxiliary valve.

4. A riveting assembly, lcomprising a iluld pres- `said hammer and said bucking bar for opening said valves, and a ilexibie cable comprising a sheath and-a core reciprocable within the sheath connecting said second manipulative means to said second valve and operable to open said valve in response to actuation of said means.

5.' A riveting assembly, comprising a iluid pressure operated hammer having a pressure iluid 111.-? let. a throttle valve manipulative from the hammer for controlling the now of fluid to said hammer, an auxiliary valve for controlling the now of fluid to said hammer, such ilow being cut oi! when either or both oi' said valves are closed thereby to prevent operationl of said hammer, a

`housing for said auxiliary valve in the form of a fitting secured in the air inlet of said hammer, said auxiliary valve being movable within said iltting to control the flow of fluid to said inlet, and a flexible cable attached to said tting and containing a longitudinally movable core in cooperative relation with said valve, said cable extending to a point remote from said hammer where movement of said core may be effected to open said valve, whereby the operation of said hammer may be controlled jointly by-the holder of the hammer and someone remote thereto.

6. A riveting assembly according to claim 5 and including a bucking bar, said hammer and said bar being under separate control and adapted to engage the rivet on opposite sides of the work, characterized in that said ilexible cable in- -terconnects said hammer and said bucking bar and is operable from said bar to open said auxiliary valve.

7. A riveting assembly, comprising a fluid vpressure operated hammer, a bucking bar, said hammer and said bar being under separate control and adapted to engage the rivet on opposite sides A of the work, first and second valves controlling the ow of fluid to said hammer, such ilow being cut od when either or both oi said valves lare closed thereby to prevent operation of said hammer, means on said hammer for opening said iirst valve, control means on said bucking bar for said second valve, said means having the form of a hand-operated lever, a flexible cable attached at its opposite ends to said hammer and said bucking bar and containing a longitudinally movable core arranged to transmit the movement of said lever to said second valve, said second valve, core and lever being connected for movement as an assembly, and spring means urging said assembly in a direction to close said valve.

JAMES A. ROBERTS. 

